Maquoit Bay, Maine Climate Change Adaptation Plan Manomet Center for Conservation Sciences Eric Walberg, AICP, William VanDoren, Jackie Sartoris May 2013 Cover photograph courtesy Steve Walker Contents 1 Site Description and History 2 Projected Climate Change Impacts 12 Ecosystem Service Vulnerabilities 12 Adaptation Recommendations by Ecosystem Service Category 12 Provisioning Services: Fish and shellfish 12 Ecosystems and Supporting Services: Biodiversity maintenance 13 Regulating Services: Water Purification and Flood Regulation 17 Conclusion 24 Endnotes Maps 3 Map 1. Location of Maquoit Bay 4 Map 2: Eelgrass Bed Cover 6 Map 3: Moluscan Shellfish Habitat 8 Map 4: Conserved Land 10 Map 5: Stream Barrier Information 14 Map 6: Impact of Sea Level Rise on Tidal Wetlands in Maquoit Bay 18 Map 7: Regional Green Infrastructure 20 Map 8: Impervious Surfaces 22 Map 9: Riparian Resources Suggested citation: Walberg, E., Sartoris, J., VanDoren, W., 2013. Climate Change Adaptation Plan for Maquoit Bay, Maine. Manomet Center for Conservation Sciences, Plymouth, MA. Support for this project was provided by The Kresge Foundation. © 2013 Manomet, Inc. All rights reserved. This report is available for download at: http://www.manomet.org/climate_solutions/Maquoit_Bay.pdf MANOmeT CENTer FOR CONservaTION ScieNces | MAY 2013 i ii MAQUOIT BAY, MaiNE CLimaTE ChaNGE AdapTATION PLAN Site Description and History Maine’s Maquoit Bay is part of an ecologically diverse estuarine complex located in northern Casco Bay and adjacent to two of Maine’s most developed towns, Brunswick (pop. 20,000) and Freeport (pop. 8,000) (Map 1). Because of its unique coastal bays and estuaries, the area has high ecological value making it one of the State’s Focus Areas of Statewide Ecological Significance.1 The Bay is known for some of the region’s most productive intertidal mud flats and large expanses of eelgrass meadows and saltmarsh (Maps 2 and 3). These systems contain state significant wildlife habitat areas for migratory birds and waterfowl, fish, invertebrates and other wildlife, including commercially important fish and shellfish.2 Historically, land use here was once dominated by large lot upland farms to the west, salt hay farming to the north, and seasonal camps on small lots extending down the east side of the Bay to Merepoint Peninsula. Recent years have seen growing development pressure with residential home development and redevelopment of the seasonal camps to year-round homes, particularly to the northeast and down the Peninsula. Efforts by several conservation organizations have protected hundreds of undeveloped acres abutting the Bay through land purchase or protective easement, primarily on the Bay’s western side (Map 4). Public interest organizations taking an active role in Maquoit Bay include State and Federal agencies (US Fish and Wildlife Gulf of Maine Coastal Program, Maine’s Department of Inland Fisheries and Wildlife, Maine Department of Marine Resources), municipalities (the Town of Brunswick, Brunswick Marine Resources Committee), non-profit organizations (Manomet Center for Conservation Sciences, Maine Audubon), and land trusts and other conservation organizations (e.g., Brunswick Topsham Land Trust, Maine Coast Heritage Trust, Casco Bay Estuary Partnership). The ability of these entities to collaborate on climate change adaptation will impact the future health and productivity of Maquoit Bay. Like many natural resources, the Bay is owned by no one entity, and no one actor alone can protect it. Maquoit Bay includes a town-owned public access boat launch, from which most local harvesters access the mudflats. Over the past two decades, local shellfish wardens have succeeded in opening more of the Bay’s highly productive clam flats to harvest by addressing substandard wastewater disposal systems of abutting residences, and by instituting a harvester service requirement that provides consistent clean up and stewardship. However, water quality is still a concern for some local officials. The Town of Brunswick enacted a 1999 referendum requiring pumpout of coastal property septic tanks every three years.3 Numerous streams drain to the Bay, but many of these are impacted by both man-made flow restrictions and diminished water quality, including excessive nutrient loading (Map 5). The Bay’s limited flushing capacity and high nutrient loading is thought to predispose it to increased risk of damaging algal bloom and severe hypoxic events.4 Local residents are beginning to see evidence of a changing climate. The Town of Brunswick’s Marine Warden stated that coastal water temperatures are the highest since the 1950’s, and notes species shifts possibly related to the warmer water. There is a higher prevalence of quahogs and invasive green crab, while native soft shell clams seem to be struggling. Although the reason is unclear, eelgrass beds have diminished within Maquoit Bay, moving further out from the mudflat area from their highest point in the 1990’s. These signs concern the Warden and others working on the coastal waters in this part of Casco Bay. Long recognized by conservation organizations and resource harvesters as worthy of protection, climate change will demand that existing and future conservation efforts factor in sea level rise, increased development pressure, and ocean acidification while ensuring that the Bay retains its high ecological value. ii MAQUOIT BAY, MaiNE CLimaTE ChaNGE AdapTATION PLAN MANOmeT CENTer FOR CONservaTION ScieNces | MAY 2013 1 Management Goals While no single set of management goals exists for the Maquoit Bay watershed, the recommended priorities identified by the steering committee of the Sagadahoc Region Rural Resource Initiative (SRRRI) mesh well with the protection of ecosystem service delivery under climate change.5 The SRRRI recommended priorities for local action are: 1. Protect water resources and riparian areas 2. Maintain large unfragmented blocks 3. Maintain connections between core habitat areas 4. Protect habitat for rare species and rare and exemplary natural communities 5. Protect farmland and support farmers 6. Protect, develop and maintain trails While the SRRRI blueprint for the region does not explicitly address climate change it does provide important background information for thinking about resiliency to climate change and appropriate adaptation actions. In particular, the recommendations to protect water resources and riparian areas through enhanced buffering and maintaining riparian forest will have multiple benefits. The recommendations to maintain blocks of undeveloped land and connections between habitat areas will support the reorganization of species and habitats that climate change will drive. A Manomet stakeholder workshop held in Brunswick, ME identified the impacts of future development, increased precipitation, and sea level rise as priority areas for adaptation planning. These topics were included as major themes in the subsequent analysis of climate change impacts and formulation of adaptation recommendations. Projected Climate Change Impacts Climate change will impact many of the highly valued natural systems that characterize the Maquoit Bay. Sea level rise will alter ocean and bay shorelines and move tidal wetlands inland. Warming ocean temperatures and ocean acidification will change the species mix in the ocean, bays and rivers and will threaten the viability of the shellfish in the region. Increasing total precipitation and increasing heavy precipitation events will increase the threat of freshwater flooding and nonpoint source pollution. (See the Manomet adaptation plan for the Sagadahoc region of Maine for an expanded discussion of recent and projected climate change impacts.) These changes will also impact the infrastructure of the region. Low lying coastal areas will suffer increased storm surge flooding and over time upgrades will be required to maintain the viability of the transportation network, utilities, homes and businesses located in vulnerable areas. 2 MAQUOIT BAY, MaiNE CLimaTE ChaNGE AdapTATION PLAN Map 1. Location of Maquoit Bay Map 1. Location of Maquoit Bay in southern Maine. MAP 1 2 MAQUOIT BAY, MaiNE CLimaTE ChaNGE AdapTATION PLAN MANOmeT CENTer FOR CONservaTION ScieNces | MAY 2013 3 Map 2: Eelgrass Bed Cover This map depicts eelgrass meadows and their proportion of cover using data provided by the Maine Department of Marine Resources through MaineGIS. Maine’s eelgrass meadows form an important marine and estuarine coastal aquatic habitat for the state. Along with other plants, eelgrass forms the base of food production in the sea. Eelgrass provides shelter for juvenile fish, and invertebrates, is a site for primary settlement of the larvae of some bivalve mollusks, and in certain locations helps to stabilize unconsolidated sediments and shorelines. MAP 2 4 TAUNTON River WATershed CLimaTE ChaNGE AdapTATION PLAN MANOMET CENTer FOR CONservaTION ScieNces | December 2012 5 Map 3: Moluscan Shellfish Habitat This map depicts molluscan shellfish habitats using data from the Maine Department of Marine Resources and distributed by MaineGIS. These are polygon datasets that contain distribution information for the molluscan shellfish species; sea scallop (Placopectin magellanicus), american oysters (Crassostrea virginica), atlantic surf clams (Spisula solidissima), blue mussels (Mytilus edulis), european oysters (Ostrea edulis), hard clams (Mercenaria mercenaria), razor clam (Ensis directus) and softshell clams (Mya arenaria) for the coast of Maine, compiled